The primary objective of this project is to obtain a better understanding of the positive attributes and limitations of videostroboscopic (VS) examination of the larynx. Of particular interest is how VS measures relate to different voice disorders and how the VS measures correlate with more traditional measures of vocal function. The research focuses on those variables (recording procedures, measurement procedures, and groups with voice disorders) which may significantly influence the interpretation of results. The specific aim of this research endeavor are: 1) To determine which endoscopic (rigid or flexible) or combination of endoscopes provide the most valid image of the larynx 2) To determine the influence of examining variables (positioning of the endoscope, extension of tongue, neck flexion, color of resultant image, examiner instructions, and use of topical anesthetics) on reliability of recordings and subsequent observations 3) To determine the best procedure for training clinicians to make valid and reliable judgments of the stroboscopic parameters of interest 4) To accurately describe vocal fold movements during phonation at different pitch and loudness secondary to neoplasms of the vocal folds, morphological changes of the vocal folds and abnormal function during phonation 5) To determine if there are lawful relationship among vibratory patterns and glottal configuration observed from the stroboscopic image and the aerodynamic acoustic, and electroglottalgraphic properties of voice 6) To determine if videostroboscopic images can be quantified relative to absolute measurements of laryngeal dimensions, relative measurements of laryngeal dimensions, and to the opening and closing timing characteristics of the glottis. Two sets of investigations will be conducted in parallel concerning the methodological aims of this proposal. The result of these investigations will serve as the basis for the third set of investigations aimed at determining if there are lawful relationships among the stroboscopic recordings and other measures of vocal function. Five groups of speakers will be studied.